Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Aim To examine variation in the phylogenetic diversity (PD) of tree communities across geographical and environmental gradients in Amazonia.Location Two hundred and eighty-three c.1ha forest inventory plots from across Amazonia.Methods We evaluated PD as the total phylogenetic branch length across species in each plot (PDss), the mean pairwise phylogenetic distance between species (MPD), the mean nearest taxon distance (MNTD) and their equivalents standardized for species richness (ses.PDss, ses.MPD, ses.MNTD). We compared PD of tree communities growing (1) on substrates of varying geological age; and (2) in environments with varying ecophysiological barriers to growth and survival.Results PDss is strongly positively correlated with species richness (SR), whereas MNTD has a negative correlation. Communities on geologically young- and intermediate-aged substrates (western and central Amazonia respectively) have the highest SR, and therefore the highest PDss and the lowest MNTD. We find that the youngest and oldest substrates (the latter on the Brazilian and Guiana Shields) have the highest ses.PDss and ses.MNTD. MPD and ses.MPD are strongly correlated with how evenly taxa are distributed among the three principal angiosperm clades and are both highest in western Amazonia. Meanwhile, seasonally dry tropical forest (SDTF) and forests on white sands have low PD, as evaluated by any metric.Main conclusions High ses.PDss and ses.MNTD reflect greater lineage diversity in communities. We suggest that high ses.PDss and ses.MNTD in western Amazonia results from its favourable, easy-to-colonize environment, whereas high values in the Brazilian and Guianan Shields may be due to accumulation of lineages over a longer period of time. White-sand forests and SDTF are dominated by close relatives from fewer lineages, perhaps reflecting ecophysiological barriers that are difficult to surmount evolutionarily. Because MPD and ses.MPD do not reflect lineage diversity per se, we suggest that PDss, ses.PDss and ses.MNTD may be the most useful diversity metrics for setting large-scale conservation priorities.
ISSN: 1366-9516

hal-01557462
https://hal.univ-lorraine.fr/hal-01557462
DOI : 10.1111/ddi.12357

Éditeur(s) : HAL CCSD
Résumé : Understanding of the mechanisms driving diversification of species is a significant way to improve the management of ecosystems, predict the impacts of climate change and understand the actual and past biodiversity level. The aim of this thesis is to understand and comprehend genetic mechanisms behind the diversification of species in the presence of gene flow. This thesis is focused on the biological model Symphonia globulifera, which presents two ecotypes: the S.globulifera, specialist of seasonally flooded lowlands and S.sp1, specialist of terra firme. These two ecotypes show low genetic differentiation, despite the presence of two apparent phenotypes. A first part of this thesis was to test the presence of local adaptation of this using reciprocal transplant experiment gardens, allowing the understanding of the ecotypes distributions in their natural habitats. Then, this local adaptation in the presence of gene flow, directed me to the regulation of gene methylation in order to see the role this brand of epigenetics can have in the divergence of the ecotypes. In a third part of the thesis, new generation sequencing of the transcriptome ecotypes in reciprocal gardens transplantations allowed me to show the evidence of gene regulation to differentiate the ecotypes. This work thesis is based on phenotype records data, AFLP genotyping and high-throughput sequencing of the transcriptome, in order to show the important value of gene regulation in the divergence of the locally adapted ecotypes, and a weak role of DNA methylation in the establishment of local adaptation.
Connaitre et appréhender les mécanismes de la diversification des espèces est important pour la gestion des écosystèmes, la prévision des impacts des changements climatiques et la compréhension de la biodiversité actuelle et passée. Le but de cette thèse est de comprendre et de déceler les mécanismes génétiques à l’origine de la diversification des espèces en présence de flux de gènes. Cette thèse se focalise sur le modèle biologique Symphonia globulifera, qui compte deux écotypes : le S.globulifera spécialiste de la terra firme et le S.sp1, spécialiste des bas-fonds. Ces deux écotypes montrent une faible différenciation génétique, malgré la présence de deux phénotypes différents.Une première étape a été de mettre en évidence la présence d’une adaptation locale au sein de cette espèce, par le biais d’une expérimentation de jardins de transplantation réciproques, permettant d’expliquer la répartition des écotypes dans leur habitat naturel. Ensuite, dans le but d’identifier les mécanismes sous-jacent à cette adaptation locale, j’ai testé l’hypothèse que la méthylation des gènes pourrait être une marque de l’épigénétique contribuant à la divergence des écotypes, par l’utilisation d’enzyme sensibles à la méthylation dans un protocole de génotypage AFLP. Enfin, un séquençage haut-débit du transcriptome des écotypes en jardins de transplantation réciproques m’a permis de mettre en évidence une expression différentielle des gènes entre les écotypes, qui pourrait expliquer les différences phénotypiques observées entre les écotypes malgré une faible différentiation génétique. Ces travaux de thèse s’appuie, ainsi, sur des données de traits phénotypiques, de génotypage AFLP et de séquençage à haut débit du transcriptome pour montrer la valeur importante de la régulation des gènes dans la divergence des écotypes adaptés localement, et un faible rôle de la méthylation de l’ADN dans l’établissement cette adaptation locale.
https://tel.archives-ouvertes.fr/tel-01405400

NNT : 2015YANE0005
tel-01405400
https://tel.archives-ouvertes.fr/tel-01405400
https://tel.archives-ouvertes.fr/tel-01405400/document
https://tel.archives-ouvertes.fr/tel-01405400/file/these_-_tinaut.pdf

Résumé : 1 - Study's goals review The management of Norway Lobster and Hake fisheries can be considered as the most important issue in the Gascogne gulf. Calculation methods used to evaluate prediction variations under various efforts and mesh constraints all pinpoint to the crucial role narrow mesh fishing plays in Hakes' Northern stock status. The involvement of Gascogne gulf Norway Lobster fisheries regarding Hakes over exploitation seems over dimensioned when comparing the size of both of these stocks. Hake stocks spread from Northern Great Britain to Northern Spain, while Norway Lobster stocks are located in the Gascogne gulf's mud flats. The biological solution is well known and consists in globally increasing mesh nets to 80mm which would bring up Hakes yield to its most. It would be unreal to pretend all parties involved in Hake stocks will come to use them. For now, it is mostly an economical issue since many vessels continue on with an exploitation scheme dating from the 60's and fish on coastal mud flats which are the most exploited zones and where their catch is detrimental to juvenile class Hakes and Norway Lobsters. Considering our limited time, this study will cover bio- economical modelisation preparation. You will therefore find a description of fisheries and an exploitation assessment based on 1986's available data. 2 - Accomplished work 2. 1 Fishery description Presenting the problems and preparing ulterior analyses was first and foremost. Norway Lobster vessels supposedly, according to evaluation models used, test immature Hakes in such a manner that all stock exploitation is jeopardized. Norway Lobster distribution is closely linked to the nature of the ocean floor since it can only build its habitat on fine sediment. Hakes' habitat is not as restrictive and is linked to food supply, especially euphausiid shrimps, so they can be found on sandy and sandy-sedimental floors. Norway Lobsters are sought by a fleet of 400 to 450 ships which characteristics widely vary according to their home port. On the northern part, fisheries are close to exploitation ports where Norway Lobsters and miscellaneous catch yield is sufficient to support an older fleet. On the southern part, the structure is diversified and flexibility usually rules, more modern vessels can easily switch their target on a seasonal or daily basis. Globally, Hakes' northern stocks are slightly on the rise. This rise is probably due to global mesh size increase, even if slight and a decrease on fishing effort where immature species are caught. Norway Lobster stocks unloading is stable or slightly lower and yields, as far as northern fishery are concerned, vary and oscillate between ±15 to ±20 % at about an average of 100 kg/day. Biological parameters used in the evaluations for each species are those used in CIEM and CEE work cells. Among those parameters, those describing growth are the greatest. For Hakes, an intermediary growth equation between males and females has been used. For Norway Lobsters, both sexes are treated separately. Simulations were carried out according to 3 types of data: Norway Lobster vessels fishing effort variations. Norway Lobster vessels mesh increase. Norway Lobster vessels fishing effort decrease or mesh increasing go along in the same direction for Hake and Norway Lobster stock production (chart A and B). Lastly, a brief study on results evaluation significance was done to modify: - the size of Hake rejects by Norway Lobster vessels. The range of sizes stays the same but the amount in each class varies according to the same percentage. - Norway Lobsters growth parameters, both values used (L» = 76 mm and k = 0.11 for males, L°° = 56 mm and k = 0.14 for females) representing the "high" hypothesis. In the first case, a 20% error rate for rejects evaluation with 60 mm mesh would only bring a 3% modification rate on global stock production. Those first results are contradicting usual evaluation conclusions and it will be necessary to recalculate by modifying the size class step. In the second case, to decrease L» and increase growth speed, in time production variations remain within usual inter annual fluctuations. In all figure cases, calculations confirming greater yield for in time production through hypothetical mesh size increase to 60 mm, are definitely well founded.
1 - Rappel des buts de l'étude La gestion des pêcheries de merlu et de langoustine peut être considérée comme le problème le plus important du Golfe de Gascogne. Les méthodes de calcul employées pour évaluer les variations de la production sous diverses contraintes d'effort et de maillage mettent toutes l'accent sur le rôle capital des pêcheries à petits maillages sur l'état du stock nord de merlu. Le niveau de responsabilité des pêcheries de langoustine du Golfe de Gascogne dans la surexploitation du merlu semble démesuré eu égard aux dimensions respectives des deux stocks. Le stock de merlu s'étend du Nord des Iles Britanniques au Nord de l'Espagne alors que le stock de langoustine est localisé aux vasièrés du Golfe de Gascogne. La solution biologique du problème est connue et tient à une augmentation généralisée des maillages à 80 mm qui amènerait le rendement du stock de merlu à son maximum. Il serait illusoire de prétendre que tous les acteurs opérant sur le stock de merlu arriveront jamais à l'utiliser. Pour le moment, le problème se pose essentiellement en termes économiques car beaucoup de navires poursuivent un schéma d'exploitation hérité des années 1960 et pèchent sur des vasièrés côtières qui sont les zones les plus exploitées et où ils effectuent leurs captures au détriment des jeunes classes d'âge de merlu et de langoustine. En raison des délais impartis, cette étude constitue la préparation à une modélisation bioéconomique. On y trouvera donc une description des pêcheries et un bilan de l'exploitation sur les données disponibles en 1986. 2 - Travaux effectués 2 . 1 Description de la pêcherie Il s'agissait avant tout de poser les problèmes et de préparer les analyses ultérieures. Les langoustiniers sont présumés, d'après les modèles d'évaluation employés, effectuer sur les immatures de merlu des prélèvements tels qu'ils mettent en danger toute l'exploitation du stock. La distribution de la langoustine est très liée à la nature du fond car elle ne peut construire son terrier que sur des fonds de vase fine. Celle du merlu est beaucoup plus large et inféodée à la recherche de nourriture, crevettes euphausiacées en particulier, on le trouve donc sur les fonds sableux à sablo-vaseux. La langoustine est recherchée par une flottille de 400 à 450 bateaux dont les caractéristiques sont très variables suivant leur appartenance géographique. Au nord, la pêcherie est proche des ports exploitants et les rendements en langoustine et en prise accessoire sont suffisants pour faire vivre une flottille ancienne. Vers le sud, la structure est très diversifiée et la flexibilité est généralement la règle et les navires de construction récente peuvent changer de cible aisément de façon saisonnière ou au cours de la même journée de pêche. Globalement, les débarquements de merlu du stock nord sont en légère hausse. Ce redressement est dû probablement aux augmentations de maillage, même légères, généralisées et à une baisse de l'effort sur les pêcheries où s'effectuent des captures d'immatures. Les débarquements de langoustine sont stables ou en légère baisse et les rendements, au moins sur la pêcherie du nord, varient avec des oscillations de ±15 à ±20 % autour d'une moyenne de 100 kg/jour. Les paramètres biologiques utilisés pour chaque espèce dans les évaluations sont ceux en usage dans les groupes de travail du CIEM et de la CEE. Parmi ces paramètres, ceux décrivant la croissance sont les plus importants. Pour le merlu une équation de croissance intermédiaire entre mâles et femelles a été utilisée. Pour la langoustine les deux sexes sont traitées séparément. Les simulations ont porté sur trois types de données : Variations de l'effort des langoustiniers Augmentation du maillage des langoustiniers La diminution de l'effort des langoustiniers ou L'augmentation de maillage agisse très exactement dans le même sens sur la production des stocks de merlu et de langoustine. Enfin une étude succincte de la sensibilité des résultats des évaluations a été effectuée pour des modifications : - de la composition en taille des rejets de merlu par les langoustiniers. L'étendue des tailles reste la même mais le nombre dans chaque classe varie selon le même pourcentage. des paramètres de croissance de la langoustine, le couple de valeurs utilisées (L» = 76 mm et k = 0.11 pour les mâles, L°° = 56 mm et k = 0.14 pour les femelles) constituant l'hypothèse "haute" Dans le premier cas, une erreur de 20 % sur l'évaluation des rejets pour un cnaillage de 60 mm n'apporterait qu'une modification de 3 % dans la production globale du stock. Ces premiers résultats sont en contradiction avec les conclusions habituelles des évaluations et il sera nécessaire de reprendre les calculs en modifiant le pas des classes de taille. Dans le deuxième cas, pour une diminution de L» et une augmentation de la vitesse de croissance, les variations de la production à terme restent à l'intérieur des fluctuations interannuelles habituelles. Dans tous les cas de figure, les calculs confirmant l'augmentation de la production à terme dans l'hypothèse d'une augmentation de maillage à 60 mm sont d'une robustesse à toute épreuve.

Droits : 1987 Ifremer
http://archimer.ifremer.fr/doc/1987/rapport-1763.pdf
http://archimer.ifremer.fr/doc/00000/1763/

Éditeur(s) : HAL CCSD Wiley
Résumé : Wood specific gravity (WSG) is a strong predictor of tree performance across environmental gradients. Yet it remains unclear how anatomical elements linked to different wood functions contribute to variation in WSG in branches and roots across tropical forests. [br/][br/]We examined WSG and wood anatomy in white sand, clay terra firme and seasonally flooded forests in French Guiana, spanning broad environmental gradients found throughout Amazonia. We measured 15 traits relating to branches and small woody roots in 113 species representing the 15 most abundant species in each habitat and representative species from seven monophyletic lineages occurring in all habitats. [br/][br/]Fiber traits appear to be major determinants of WSG, independent of vessel traits, in branches and roots. Fiber traits and branch and root WSG increased from seasonally flooded species to clay terra firme species and lastly to white sand species. Branch and root wood traits were strongly phylogenetically constrained. Lineages differed in wood design, but exhibited similar variation in wood structure across habitats. [br/][br/]We conclude that tropical trees can invest differently in support and transport to respond to environmental conditions. Wind disturbance and drought stress represent significant filters driving tree distribution of Amazonian forests; hence we suggest that biophysical explanations should receive more attention.
ISSN: 0028-646X

hal-01195075
https://hal.archives-ouvertes.fr/hal-01195075
PRODINRA : 269680
PUBMED : 24329812

Éditeur(s) : HAL CCSD
Résumé : International audience
Understand the dynamics of the fresh-salt water interface in aquifers is a key issue to comprehend mixing processand to quantity the discharge of nutrients in to coastal areas. In order to go beyond the current knowledge inthis issue an experimental site has been set up at the alluvial aquifer Riera Argentona (Barcelona – Spain). Thesite comprises 16 shallow piezometers installed between 30 and 90 m from the seashore, with depths rangingbetween 15 and 25 meters. The seawater interface is being monitored using several techniques, the combinationof which will help us to understand the spatial and temporal behaviour of the mixing zone and the geochemicalprocesses occurring there. Specially the deepest piezometers are equipped with electrodes in order to performcross-hole electrical resistivity tomography (CHERT). In addition, all piezometers are also equipped with FiberOptic cable to perform distributed temperature measurements. Two single steel armoured fibre optic cable lines ofaround 600m length were installed in all boreholes. The objective is to use the cable both as passive and activetemperature sensor. The first is being done for the continuous monitoring of temperature whereas; the secondprovides a higher temperature resolution used to monitor field experiments.Periodic CHERT measurements are carried out between the piezometer equipped with electrodes, resultingin parallel and perpendicular vertical cross sections of the site resistivity. The position of the fresh-salt waterinterface can be identified due to the resistivity contrast between the saline and fresh water. Preliminary resultsof periodic distributed temperature measurements will be also be used to monitor the position of the mixing zonethanks to the contrast and seasonal temperature changes. Periodic down-hole EC profiles will be used to validatethe method.AcknowledgementsThis work was funded by the projects CGL2013-48869-C2-1 y CGL2013-48869-C2-2-R of the Spanish Government.We would like to thank SIMMAR (Serveis Integrals de Manteniment del Maresme) and the ConsellComarcal del Maresme in the construction of the research site
European Geosciences Union General Assembly 2016
Vienne, Austria

insu-01308757
https://hal-insu.archives-ouvertes.fr/insu-01308757

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this study, we report the cloning of three transcripts for leptin receptor in the European sea bass, a marine teleost of economic interest. The two shortest variants, generated by different splice sites, encode all functional extracellular and intracellular domains but missed the transmembrane domain. The resulting proteins are therefore potential soluble binding proteins for leptin. The longest transcript (3605 bp), termed sblepr, includes all the essential domains for binding and transduction of the signal. Thus, it is proposed as the ortholog for the human LEPR gene, the main responsible for leptin signalling. Phylogenetic analysis shows the sblepr clustered within the teleost leptin receptor group in 100% of the bootstrap replicates. The neuroanatomical localization of sblepr expressing cells has been assessed by in situ hybridization in brains of sea bass of both sexes during their first sexual maturation. At histological level, the distribution pattern of sblepr expressing cells in the brain shows no clear differences regarding sex or reproductive season. Transcripts of the sblepr have a widespread distribution throughout the forebrain and midbrain until the caudal portion of the hypothalamus. A high hybridization signal is detected in the telencephalon, preoptic area, medial basal and caudal hypothalamus and in the pituitary gland. In a more caudal region, sblepr expressing cells are identified in the longitudinal torus. The expression pattern observed for sblepr suggests that in sea bass, leptin is very likely to be involved in the control of food intake, energy reserves and reproduction
ISSN: 0016-6480

hal-01290500
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01290500
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01290500/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01290500/file/Leptin%20receptor%20gene%20in%20the%20European%20sea%20bass%20postprint.pdf
DOI : 10.1016/j.ygcen.2016.03.017

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Trade-offs among functional traits reveal major plant strategies that can give insight into species distributions and ecosystem processes. However, current identification of plant strategies lacks the integration of root structural traits together with leaf and stem traits. 2. We examined correlations among 14 traits representing leaf, stem and woody root tissues. Traits were measured on 1084 individuals representing 758 Neotropical tree species, across 13 sites representative of the environmental variation encompassed by three widespread habitats (seasonally flooded, clay terra firme and white-sand forests) at opposite ends of Amazonia (French Guiana and Peru). 3. Woody root traits were closely aligned with stem traits, but not with leaf traits. Altogether leaf, stem and woody root traits delineated two orthogonal axes of functional trade-offs: a first axis defined by leaf traits, corresponding to a leaf economics spectrum, and a second axis defined by covarying stem and woody root traits, corresponding to a wood economics spectrum. These axes remained consistent when accounting for species evolutionary history with phylogenetically independent contrasts. 4. Despite the strong species turnover across sites, the covariation among root and stem structural traits as well as their orthogonality to leaf traits were strongly consistent across habitats and regions. 5. We conclude that root structural traits mirrored stem traits rather than leaf traits in Neotropical trees. Leaf and wood traits define an integrated whole-plant strategy in lowland South American forests that may contribute to a more complete understanding of plant responses to global changes in both correlative and modelling approaches. We suggest further meta-analyses in expanded environmental and geographic zones to determine the generality of this pattern.
ISSN: 0269-8463

hal-01032415
https://hal.archives-ouvertes.fr/hal-01032415
DOI : 10.1111/j.1365-2435.2012.02020.x

Éditeur(s) : Université d'Angers
Résumé : In oyster farming areas, organic matter fluxes toward sediment is increased. Pacific oysters (Crassostrea gigas) reject organic-rich faeces and pseudofaeces as a result of filtration process. Organic matter can be consumed by benthic fauna, but in excess it can entails the reduction of benthic faunal species richness, abundance and biomass. Organic matter degradation also induces hypoxic (or anoxic) conditions in the sediment, and production of ammonia and sulfides in toxic concentrations. The main objective of this study is to assess the effects of oyster farming on benthic intertidal ecosystems in the Pertuis Charentais. Benthic macrofauna, living (stained) foraminifera, and physicochemical characteristics of the water column and sediment were used as indicators to evaluate these effects. A multidisciplinary approach was conducted across the Pertuis Charentais at 3 different spatial scales: an oyster trestle (micro-scale), an oyster culture area (meso-scale) and various sites across the Pertuis Charentais (macro-scale). The study was also realised at 4 different temporal scales: some months for the spatial micro-scale, every two weeks for 2 years at meso-scale and once per season during one year at macro-scale. In this study, I found that oyster farming enriches sediment in fine particles, organic matter (up to 12 %), particulate organic carbon (15-20 µg mg 1) and leads to high microphytobenthic biomass. Moreover, the association of seasonnal warming (during spring and summer), remineralisation of accumulated organic matter and short-term hypoxic conditions leads to sulfides and ammonium production. Consequently, the benthic biodiversity decreases and the population dynamic is disturbed. The population dynamic disturbance is characterised by fast abundance rises followed by high mortality rates. In these conditions, tolerant benthic macrofaunal (Cirratulidae, Spionidae and Capitellidae) and foraminiferal (Ammonia tepida and Cribroelphidium gunteri) species are promoted. AMBI index confirms "medium" ecological quality of oyster farming areas. On the contrary, across the control sites, sensible species are maintained (Amphipods, Rosalina cf. vilardeboana). Comparison of oyster farming techniques shows that on-bottom culture is less disturbing for benthic ecosystem than off-bottom culture. Axial tomodensitometry, an innovative method, was used to describe in 3D the sedimentary column organisation. I show that oyster farming modifies the sedimentary column functioning. Indeed, the macrofaunal diversity decrease leads to the modification of the functional diversity of assemblages. Thus, the vertical distribution of living foraminifera is limited in oyster farming areas, because their distribution is tightly related to macrofaunal bioturbating modes.
Dans les zones ostréicoles, les flux de matière organique sont importants, l'huître Crasssotrea gigas rejetant sous forme de pseudo-fécès et de fécès de grandes quantités de matière organique. De ce fait, bien que cette matière organique puisse être consommée par la faune benthique, sa surabondance peut provoquer une réduction de la richesse spécifique, de l'abondance et de la biomasse et provoquer sur le plan des processus biogéochimiques des déplétions en oxygène et l'apparition de substances comme l'ammonium et les sulfures dont les concentrations peuvent devenir toxiques. L'objectif principal de cette étude était donc de déterminer l'impact de l'ostréiculture, grâce à plusieurs indicateurs, sur le compartiment benthique d'un écosystème littoral comme les pertuis charentais. Pour évaluer ces effets, la macrofaune benthique et les foraminifères vivants benthiques ont été utilisés en association avec des mesures des paramètres physico-chimiques de la colonne d'eau et du sédiment. Une approche pluridisciplinaire a ainsi été menée dans les pertuis charentais à trois échelles spatiales différentes : à l'échelle d'une table ostréicole (micro-échelle), à l'échelle d'un site ostréicole (méso-échelle) et à l'échelle des pertuis charentais (macro-échelle). Dans les trois cas, un suivi dans le temps a été associé à une étude de distribution spatiale, quelques mois à micro-échelle, tous les quinze jours pendant deux années à méso-échelle et une fois par saison pendant une année à macro-échelle. Ces différentes approches ont permis d'avoir une vision pertinente de la dynamique et de la réponse fonctionnelle de la faune benthique aux changements induits par la présence de l'ostréiculture. La présence des cultures ostréicoles dans les pertuis charentais enrichit les sédiments en particules fines, en matière organique (12 %), en carbone organique particulaire (15-20 µg mg-1) et favorise une production microphytobenthique élevée. Pendant la période chaude de l'année printemps-été, la reminéralisation de la matière organique accumulée associée à des hypoxies temporaires a favorisé la production de sulfures et d'ammonium. Dans les stations soumises à l'ostréiculture, la diversité des assemblages diminue. La dynamique des espèces est caractérisée par des augmentations rapides des abondances suivies d'épisodes de mortalité. Les espèces tolérantes de la macrofaune benthique (Cirratulidae, Spionidae et Capitellidae) et des foraminifères vivants benthiques (Ammonia tepida et Cribroelphidium gunteri) sont favorisées. Le calcul de l'indice AMBI confirme la qualité écologique moyenne de ces sites. Au contraire, dans la station témoin, les espèces sensibles sont favorisées (Amphipodes, Rosalina cf. vilardeboana). La comparaison de la technique de culture sur table et de culture à plat a montré que la culture des huîtres à plat est moins perturbante pour le milieu. L'étude de la bioturbation a montré l'influence qui existe entre le mode de bioturbation des différents groupes de la macrofaune et la répartition verticale des foraminifères vivants dans la colonne sédimentaire. La diminution de la diversité des assemblages de la macrofaune dans les zones soumises à l'ostréiculture modifient la diversité fonctionnelle de ces assemblages et affectent le fonctionnement de la colonne sédimentaire, limitant la répartition verticale des foraminifères dans ces zones.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2007/these-2582.pdf
http://archimer.ifremer.fr/doc/00000/2582/

Éditeur(s) : HAL CCSD Wiley
Résumé : The intensification of the hydrological cycle, with an observed and modeled increase in drought incidence and severity, underscores the need to quantify drought effects on carbon cycling and the terrestrial sink. FLUXNET, a global network of eddy covariance towers, provides dense data streams of meteorological data, and through flux partitioning and gap filling algorithms, estimates of net ecosystem productivity (FNEP), gross ecosystem productivity (P), and ecosystem respiration (R). We analyzed the functional relationship of these three carbon fluxes relative to evaporative fraction (EF), an index of drought and site water status, using monthly data records from 238 micrometeorological tower sites distributed globally across 11 biomes. The analysis was based on relative anomalies of both EF and carbon fluxes and focused on drought episodes by biome and climatic season. Globally P was ≈50% more sensitive to a drought event than R. Network-wide drought-induced decreases in carbon flux averaged −16.6 and −9.3 g C m−2 month−1 for P and R, i.e., drought events induced a net decline in the terrestrial sink. However, in evergreen forests and wetlands drought was coincident with an increase in P or R during parts of the growing season. The most robust relationships between carbon flux and EF occurred during climatic spring for FNEP and in climatic summer for P and R. Upscaling flux sensitivities to a global map showed that spatial patterns for all three carbon fluxes were linked to the distribution of croplands. Agricultural areas exhibited the highest sensitivity whereas the tropical region had minimal sensitivity to drought. Combining gridded flux sensitivities with their uncertainties and the spatial grid of FLUXNET revealed that a more robust quantification of carbon flux response to drought requires additional towers in all biomes of Africa and Asia as well as in the cropland, shrubland, savannah, and wetland biomes globally.
ISSN: 1354-1013

hal-01032076
https://hal.archives-ouvertes.fr/hal-01032076
DOI : 10.1111/j.1365-2486.2009.01991.x

Éditeur(s) : Springer
Résumé : Two recurring syndromes threaten the viability of the shrimp industry in New Caledonia, which represents the second largest export business. The "Syndrome 93" is a cold season disease due to Vibrio penaeicida affecting all shrimp farms, while the "Summer Syndrome" is a geographically restricted vibriosis caused by a virulent lineage of Vibrio nigripulchritudo. Microbiological procedures for diagnosis of these diseases are time-consuming and do not have the ability to discriminate the range of virulence potentials of V. nigripulchritudo. In this study, we developed a multiplex PCR method to simultaneously detect these two bacterial species and allow for pathotype discrimination. The detection limits of this assay, that includes an internal amplification control to eliminate any false-negative results, were determined at 10 pg purified DNA and 200 cfu/ml. After confirming the effectiveness of our method using experimentally infected animals, its accuracy was compared to standard biochemical methods during a field survey using 94 samples collected over 3 years from shrimp farms encountering mortality events. The multiplex PCR showed very high specificity for the detection of V. penaeicida and V. nigripulchritudo (inclusivity and exclusivity 100%) and allowed us to detect the spreading of highly pathogenic isolates of V. nigripulchritudo to a farm adjoining the "Summer Syndrome area." This assay represents a simple, rapid, and cost-effective diagnostic tool for implementing timely risk management decisions but also understanding the seasonal and geographical distribution of these pathogens.
Microbial Ecology (0095-3628) (Springer), 2012-01 , Vol. 63 , N. 1 , P. 127-138

Droits : Springer Science+Business Media, LLC 2011
http://archimer.ifremer.fr/doc/00063/17398/15169.pdf
DOI:10.1007/s00248-011-9951-3
http://archimer.ifremer.fr/doc/00063/17398/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Multiproxy analyses were performed on core MS27PT recovered in hemipelagic sediments deposited on the Nile margin in order to reconstruct Nile River palaeohydrological fluctuations during the last 100,000 years. The strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source, oscillating between a dominant aeolian Saharan contribution during arid periods and a dominant Nile River contribution during pluvial periods. Iron content shows a strong correlation with strontium and neodymium isotopes. This allows the use of a high-resolution continuous Fe record as a proxy of Blue Nile sediment input over the last 100,000 years. The detailed Fe record, with approximately 10 years resolution during pluvial periods, is consistent with subtropical African records of well-dated lake level fluctuations and thus constitutes a first continuous high resolution record of the East African monsoon regime intensity over Ethiopia.;The detailed Fe record shows the two main known pluvial periods attributed to strengthening of the African monsoon over Ethiopia, the Nabtian period from 14 to 8 ka cal BP and the Saharan period from 98 to 72 ka BR For the first time, the last glacial period (Marine Isotope Stage (MIS) 2,3 and 4) is documented with a continuous record showing large oscillations between high and low East African palaeo-monsoon regimes.;The end of the Nabtian period occurred at 8 ka in core MS27PT, i.e. much earlier than on the East Equatorial African region where it ended around 5.5 ka. We interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the Eastern Ethiopian Highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka. During the last glacial period, two wet periods are present around 60-50 ka BP and 38-30 ka BP. These two humid periods are in phase with the rise of atmospheric CH4 concentrations suggesting that wetland tropical African area was one of the sources of the atmospheric CH4 during the MIS 3. During the Last Glacial Maximum and MIS 4, high Saharan aeolian influxes in phase with records of aeolian dust deposited in East Antarctica are documented. This study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low- and high-latitude climate variability at millennial timescales.
ISSN: 0277-3791

hal-00496481
https://hal.archives-ouvertes.fr/hal-00496481
DOI : 10.1016/j.quascirev.2010.02.006

Éditeur(s) : Elsevier
Résumé : Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is found in relict regressive sands at the outershelf. Their deposition occurred just after the onset of the post-glacial sea level rise and the concomitant sediment starvation of the Rhone deep sea turbiditic system until recently. Whilst canyons are fed with sand by strong seasonal hydro-sedimentary dynamics on the outershelf, the emplacement of post-glacial turbidites is not controlled by sea level changes but probably by the periodic flushing of the canyons. Our study revealed that this low energy aseismic margin undergoes significant transport of sand, down to the base of slope, during the sea-level rise and the Holocene highstand.
Marine Geology (0025-3227) (Elsevier), 2009-02 , Vol. 257 , N. 1-4 , P. 65-86

Droits : 2009 Published by Elsevier Ltd.
http://archimer.ifremer.fr/doc/2009/publication-6316.pdf
DOI:10.1016/j.margeo.2008.10.013
http://archimer.ifremer.fr/doc/00000/6316/

Résumé : The principal objective of the work carried out in the deep waters adjoining the island shelf around Martinique between July 1991 and april 1992 was to establish an initial inventory of potentially exploitable deep benthic resources.The cylindrical lobster pot used during fishing experiments allowed the catch of a varied carcinological marine organisms of which six species at least have economic interest : 5 species of shrimp all belonging to the sub-order of Caridea of the Pandalidae family : Plesionika edwardsi, P. (macropoda) polyacanthomerus, P.laevis, Heterocarpus ensifer and H.laevigatus, and one species of prawn of the Nephropidae family : Eunephrops cadenasi. The yields, compared to those of commercial fishermen, were medium or good for Plesionika edwardsi and P. (macropoda) polyacanthomerus between depths of 200 - 300 metres ; for Plesionika laevis and Eunephrops cadenasi in the vicinity 500 metres ; for Heterocarpus laevigatus below 700 metres. The species Heterocarpus ensifer , of which the vertical distribution is very spread out from 170 to 600 metres, seems divided into two populations which provide good yields about 300 metres and below of 450 mètres. Data on the environment and the biology of the species where also established, especially on growth and breeding. For example growth of the pandalids is relatively rapid and their life cycle rather short, between three and four or five years according to the species. At least 2 principal egg-laying seasons occur in the annual cycle. Information is given on the isopoda of the family of Cirolanidae, Bathynomus giganteus, which could eventually, under certain conditions, become of interest to the fishermen.
Les pêches expérimentales effectuées dans les eaux profondes circum-martiniquaises,attenantes au plateau insulaire, entre juillet 1991 et avril 1992, avaient pour principal objectif d'établir un premier inventaire des ressources benthiques profondes potentiellement exploitables. Le casier cylindrique , a permis la capture d'une faune carcinologique variée dont 6 espèces au-moins ont présenté un intérêt économique : 5 espèces de crevettes appartenant toutes à l'infra-ordre des Caridea, famille des Pandalidae, Plesionika edwardsi, P. (macropoda) polyacanthomerus, P.laevis, Heterocarpus ensifer et H.laevigatus, et une espèce de langoustine, famille des Nephropidae: Eunephrops cadenasi. Les rendements, comparés à ceux des professionnels, sont moyens ou bons pour Plesionika edwardsi et P.(macropoda) polyacanthomerus entre 200 et 300 mètres de profondeur; pour Plesionika laevis et Eunephrops cadenasi autour de 500 mètres ; pour Heterocarpus laevigatus en-dessous de 700 mètres. L'espèce Heterocarpus ensifer dont la distribution verticale est très étendue, de 170 à 600 mètres, semble divisée en 2 populations pour lesquelles de bons rendements peuvent être obtenus vers 300 mètres et en-dessous de 450 mètres. Des données sur l'environnement et la biologie des espèces ont également été acquises, notamment sur la croissance et la reproduction. Ainsi la croissance des pandalides est relativement rapide et leur longévité plutôt courte, entre 3 et 4 ou 5 années selon les espèces. Au moins deux pontes principales interviennent sur un cycle annuel. Des informations sont données sur l'isopode de la famille des Cirolanidae, Bathynomus giganteus, qui pourrait éventuellement, sous certaines conditions, présenter un intérêt pour les pêcheurs.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1994/rapport-1540.pdf
http://archimer.ifremer.fr/doc/00000/1540/

Résumé : After a period of rapid development of the sites (an increase in both reared surface area and production), tropical shrimp aquaculture is currently being faced with critical problems due to economical and ecological constraints. In many countries with favourable conditions for shrimp aquaculture such as indonesia or Vietnam, sites are often badly selected and/or over-exploited. This conducts to sorne extent to decreases or collapses in the production due to the difficulty in predicting the maximum production capacity of the sites. Furthermore, it appears that production sustainability depends on many factors among which socio-economy and ecolo gy are of prime importance. The STD3 project titled « Assessment of tropical shrimp aquaculture impact on the environment in tropical countries using hydrobiology, ecology and remote sensing as helping tools for diagnosis )) was initiated in 1994, with the aim to study the sustainability of marine shrimp aquaculture in tropical areas, main! y Indonesia and Vietnam, through the following tasks: (i) improve site selection and study the impact of aquaculture on marine environments presenting a variable sensitivity to organic sewage, (ii) analyse the socio-economical aspects and profitability of the aquaculture industry and of common resources (iii) use remote sensing and geographical data bases for diagnosis and monitoring of site degradation (iv) reinforce the capacity of Asian scientists through training. Severa! aquaculture sites have been investigated in the Lampung region (South Sumatra, Indonesia), the Mekong delta (Vietnam) and on the West coast of New-Caledonia, providing a large range of typical ecosystems encountered in Asia and in the Pacifie, from coralline sites to coastal plains with mangrove and deltaic areas. The study concerned the spatial structure and seasonal influence of these ecosystems, the temporal variation during the course of the project (3 years) and the relation between the ecological structure and farm productions. Remote sensing provides a synoptic vision over large land expanses. Severa! scenes were processed for landuse mapping using conventional classification techniques. Concerning water quality assessment, a general relation for the Java sea was found between image and field data in terms of total suspended matter. Applying this relation to a new site in Sumatra has provided an initial approach to water type and, together with land use mapping, a preliminary assessment of the suitability of the area to shrimp aquaculture development. Socio-economic research has been focused on the identification ofneeds for collective action, including public policy, in the perspective of shrimp farming sustainability. The main concern is in the regulation of shrimp farming intensification and extensification at the scale of coastal ecosystemic entities in a common property resource management perspective. The common considered here is coastal water quality. Comparing the local development profiles and the institutional grounds for the design and implementation of collective management rules shows that variables such as land tenure system, farm owner socio-economic profile, social homogeneity or heterogeneity of the farmers are key factors to analyse the potential for sustainability. The defmition of water quality and the possible means to ensure its collective management are discussed. The main conclusion is that the economie incentives to farming development are strong but there is no significant difference among traditional, semi-intensive and intensive systems in terms of economie efficiency or wealth distribution. The description of the functioning of the different kinds of ecosystems make it possible to give an advice concerning the positioning of the activity inside the ecosystem, and furthermore to have a reference state in order to determine the impact of the activity on the coastal environnement. This impact can be summarized as an increase in the concentration of total suspended matt€?r, of particulate organic matter and of sulfate reducing bacterias. This organic ma~.er is either issued from rearing activities or from telluric origine, due to mangrove eradication when building the ponds. An evaluation of the relationship existing between productivity and characteristics of each ecosystem bas been conducted by correlating ecological indicators data (concentration of total suspended matter, particulate organic matter, chlorophyll, percentage of pheopigments in total pigments and cyanobacteria and sulfatereducing bacteria in water and sediments) with the average production of the farms. This comparison lead to the compilation of a scale of observed production integrating the range of these environmental parameters with shrimp production levels, bound to facilitate the positioning of shrimp farming in relation with the confmement leve! of each ecosystem. Lastly, ali geographie data originated from the various compartments of the study have been geo-referenced and loaded into a geographical information system. This allows to display any query made on spatial variables and their related statistical data, including the ir variations over the last few years and to reveal patterns and phenomena otherwise not obvious.
Le programme mis en oeuvre par la DRV (Paris, CREMA-L'Houmeau, DELIAO Brest, COP Tahiti, GIE/RA Nouvelle Calédonie), dans le cadre d'un projet européen STD3 «(Sciences et Technique au Service du Développement», en collaboration avec l'Université de Montpellier II, l'Ecole Nationale d'Agronomie de Rennes, l'ITC (Hollande), l'Institut Océanographique de Nha Trang (Vietnam), le BADC de Jepara et le BPPT de Jakarta (Indonésie), avait pour but la mise au point de méthodes permettant d'améliorer la sélection des sites ainsi que le suivi du développement et de l'impact de l'aquaculture des crevettes Péneides en milieu tropical pour éviter la surexploitation. Quatre axes de recherche ont été défmis : a) identifier la nature et quantifier les rejets de déchets issus de ce type d'aquaculture, b) définir les caractéristiques écologiques des écosystèmes susceptibles d'accueillir l'activité aquacole et suivre leur évolution sous l'influence des rejets, c) déterminer l'influence de la gestion des fermes et des ressources (aspects économiques) sur les performances de productivité, d) déterminer la capacité de la télédétection comme outil de diagnostic d'impact à l'échelle de la région, e) mener un programme de formation d'étudiants et jeunes chercheurs Vietnamiens et Indonésiens.

Droits : 1998 Ifremer
http://archimer.ifremer.fr/doc/00132/24357/22357.pdf
http://archimer.ifremer.fr/doc/00132/24357/

Éditeur(s) : HAL CCSD John Wiley & Sons
Résumé : International audience
Kisspeptins are now considered key players in the neuroendocrine control of puberty and reproduction, at least in mammals. Most teleosts have two kiss genes, kiss1 and kiss2, but their sites of expression are still poorly documented. As a first step in investigating the role of kisspeptins in the European sea bass, a perciform fish, we studied the distribution of kiss1 and kiss2-expressing cells in the brain of males and females undergoing their first sexual maturation. Animals were examined at early and late in the reproductive season. We also examined the putative expression of estrogen receptors in kiss-expressing cells and, finally, we investigated whether kisspeptins are expressed in the pituitary gland. We show that kiss1-expressing cells were consistently detected in the habenula and, in mature males and females, in the rostral mediobasal hypothalamus. In both sexes, kiss2-expressing cells were consistently detected at the level of the preoptic area, but the main kiss2 mRNA-positive population was observed in the dorsal hypothalamus, above and under the lateral recess. No obvious sexual differences in kiss1 and kiss2 mRNA expression were detected. Additional studies based on confocal imaging clearly showed that most kiss1 mRNA-containing cells of the mediobasal hypothalamus strongly express ERα and slightly express ERβ2. At the pituitary level, both sexes exhibited kiss1 mRNA expression in most FSHβ-positive cells and never in LHβ-positive cells.
ISSN: 0092-7317

hal-00877326
https://hal.archives-ouvertes.fr/hal-00877326
PUBMED : 22886357
DOI : 10.1002/cne.23211

Éditeur(s) : Elsevier
Résumé : The accumulation of nine heavy metals in fine-grained sediments from the mangrove fringed coast of French Guiana is evaluated. The dynamic features of the South American tropical coastline, from the Amazon to the Orinoco Rivers, result in mangrove sediments being alternately submitted to phases of erosion and net sedimentation a few tens of years long. This process influences the distribution of the heavy metals associated with these frequently re-mobilized deposits. Sedimentary cores and mangrove plant samples were collected, at different seasons, in various swamps characterized by different properties (content of sedimentary organic matter, distance from sea water and fresh water). The ranges of measured concentrations expressed in mu mol g(-1) were the following: Cu (0.06 to 0.61), Co (0.12 to 0.68), Pb (0.08 to 0.18), Ni (0.32 to 0.76), Cr (0.61 to 1.40), Zn (1.25 to 5.94), Mn (4.36 to 45.4) and Fe (441 to 1128). No differences were found between sediments from mangroves developing upstream and downstream of urban areas, i.e. Cayenne and Kourou. This suggests that the content of mangrove sediments in heavy metals along the coastline of French Guiana is essentially the result of the continuous alternation of accumulation and transport phases occurring upstream after departing from the Amazon watershed. The sources of this heavy metals content are thus difficult to identify. However it is well known that the alluvium produced by the natural erosion of the Amazonian soils is naturally enriched in mercury. Also, the run-off from gold mining activities is known to contribute to mercury pollution. Ranges in total Hg were between 0.15 and 2.57 nmol g(-1), with mean values close to 0.41 nmol g(-1), and were clearly correlated with total organic carbon except for some outstanding high values, which may be a result of rapid geochemical changes. Heavy metal concentrations showed variations with depth. The redox conditions and the decay processes affecting the organic matter control the cycling of iron and manganese, which in turn control the concentrations and associations of heavy metals. These preliminary results suggest that the variations in heavy metal content with depth or between mangrove areas result largely from diagenetic processes rather than changes in metal input resulting from local human activities. (c) 2005 Elsevier B.V. All rights reserved.
Marine Chemistry (0304-4203) (Elsevier), 2006 , Vol. 98 , N. 1 , P. 1-17

Droits : 2005 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/2006/publication-1041.pdf
DOI:10.1016/j.marchem.2005.06.001
http://archimer.ifremer.fr/doc/00000/1041/

Éditeur(s) : HAL CCSD
Résumé : International audience
The challenge is to implement research that can estimate the consequences ofclimate changes in terms of impact on terrestrial environments and resources.Emphasis should be placed on regions dependent on natural resources and forwhich demographic pressure is strong. Simulations obtained from climate modelprojections (using different Representative Concentration Pathways (RCPs))predict that the Mediterranean basin and its southern periphery are particularlyvulnerable to water resources and environmental impact (IPCC, AR5, 2013).An annual rainfall decrease by 30% is found for the projection period 2070-2099(IPCC, AR5, 2013) associated with a decrease in water resources by 30 to 50%(Milano, 2012). In addition, several studies using regional atmospheric modelsindicate an increase in the precipitation inter-annual variability with extremeevents and a spatial heterogeneous signature, superimposed on a decrease in thetotal precipitation amount (Giorgi and Lionello, 2008; Raible et al. 2010).Currently, regional climate projections are highly sensitive to the climate modelused. In particular, spatial resolution as well as local climate conditions seemto impact significantly on the simulations (Jacob et al. 2014).The Mediterranean region, at the interface between arid and temperate climateswith several mountainous areas, is a complex climate system affected by theinteractions between mid-latitude and sub-tropical processes. In this context,Morocco, located at the transition between a temperate climate to the North anda tropical climate to the south constitutes a key area for an impact and sensitivitystudy to global climate changes. The climate is influenced by the Atlantic Ocean,the Mediterranean Sea and the Sahara, together with a very steep orography inthe Atlas region. The precipitation distribution is therefore characterised by greatspatial variability, and exhibits a marked seasonality, a strong inter-annualvariability (Ouda et al. 2005) and in general a pronounced gradient from northto south and west to east. At a broader scale, Morocco is located on the subtropicalsubsidence path and between the Acores High and the Saharan Low (Agoussine,2003). Several studies have also identified strong links with inter-annualprecipitation variability and NAO index (Knippertz, 2003) as well as remoteclimate modes (Esper et al. 2007).Continental climate variability at a local/regional scale, if it is to be integratedin climate predictions, needs to be supported by long-term observation.Meteorological stations in Morocco provide climatic data mainly for the last40 years with only a few stations located in the mountainous region (Tramblayet al. 2012; 2013; Driouech et al. 2010). This climate database is also supportedby the IAEA network providing stations for which isotope tracers have beenapplied to daily/monthly rain and water vapour samples over 2 to 3 years between2000 and 2004. Besides the poor coverage of instrumented areas, lacustrinesystems can provide a climatic data set that offers access to short and long-termtime series of climate parameters when knowledge of modern lake water balanceis combined with lacustrine sedimentary-climate records. Lake sediment recordsideally provide high resolution climate/environmental information of the last10,000 years (Magny et al. 2013). This time interval (corresponding to theHolocene) is a key period to investigate short and long-term climate variabilityand to improve prediction in a warming climate.In this study we present an integrated approach focusing on a mountainous lake(Aguelmam Azigza). The modern lake system study is based on site monitoring(2012-2016) and available regional hydro-climatic data. These data show thatlake level changes during the instrumented period were mainly driven byprecipitation following the high inter-annual variability. These data are thencompared with accurately dated short sediment cores retrieved in the same lake.Micro-scale geochemical and sedimentological analyses of these sequencesenable us to identify various sedimentary facies that can be linked with periodsof high (low) lake levels over the past decades.
The Mediterranean Region under Climate ChangeLa méditerranée face au changement climatique

insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690/document
https://hal-insu.archives-ouvertes.fr/insu-01394690/file/Vidaletal.2016-COP22-Chap1.pdf

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : For most fisheries, increasing the local production of pelagic fish is the main objective of Fish Aggregating Devices (fads). This does not rule out the existence of a larger-scale impact, especially on the migratory behaviour of fish. The analysis of data collected during 25 experimental fishing surveys around Martinique between 1995 and 1997 has led to the hypothesis that fads influence the migratory behaviour of young dolphinfish. Unlike recent studies of dolphinfish migration in the Caribbean, which tend to show an annual migration pattern with a seasonal passage through the French West Indies, the experimental fishing surveys done over more than a year on a monthly basis on a single cohort, show that the migratory pattern of part of the regional stock could be disrupted. This analysis has made it possible to estimate an average growth rate for this species during the first year of life.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15321/12635.pdf
http://archimer.ifremer.fr/doc/00042/15321/

Éditeur(s) : Springer
Résumé : The Var turbidite system is a small sandy system located in the Ligurian Basin. It was deposited during the Pliocene-Quaternary in a flat-floored basin formed during the Messinian salinity crisis. The system was fed through time by the Var and Paillon canyons that connect directly to the Var and Paillon rivers. It is still active during the present sea-level highstand. Two main mechanisms are responsible for gravity-flow triggering in the Var turbidite system: (1) mass-wasting events affect mainly the upper part of the continental slope, in areas where volumes of fresh sediment delivered by rivers are highest, and result from the under-consolidation state of slope sediments and earthquakes, and (2) high-magnitude river floods resulting from melting of snow and convective rainfall during fall and spring seasons, and generating hyperpycnal turbidity currents at river mouths when the density of freshwater transporting suspended particles exceeds that of ambient seawater. Failure- and flood-induced gravity flows are involved through time in the construction of the Var Sedimentary Ridge, the prominent right-hand levee of the Var system, and sediment waves. Processes of construction of both the Var Ridge and sediment waves are closely connected. Sandy deposits are thick and abundant in the eastern (downchannel) part of the ridge. Their distribution is highly constrained by the strong difference of depositional processes across the sediment waves, potentially resulting through time in the individualization of large and interconnected sand bodies.
Geo-Marine Letters (0276-0460) (Springer), 2006-12 , Vol. 26 , N. 6 , P. 361-371

Droits : 2006 Springer
http://archimer.ifremer.fr/doc/2006/publication-2258.pdf
DOI:10.1007/s00367-006-0047-x
http://archimer.ifremer.fr/doc/00000/2258/

Éditeur(s) : Université Paris 7 – Denis Diderot
Résumé : Sea surface salinity (SSS) influences numerous oceanic phenomena, for instance surface water ventilation, deep water formation and thermohaline circulation. SSS also controls some ocean-atmosphere coupled processes, such as the intensity of freshwater flux and the penetration of heat flux and turbulence. Salinity is more difficult to measure than temperature from in situ surveys, which results in 20 times less data being currently available. Moreover, sea surface temperature (SST) is routinely estimated from satellites, which is not possible yet for SSS. Two space missions will fill this gap soon: SMOS from the European Space Agency and Aquarius/SAC-D from NASA and CONAE. To contribute to the SMOS project, we propose a method for estimating SSS from current satellite observations and for studying the mechanisms governing its variability. We developed a simplified model of the ocean mixed layer, based on the "slab mixed layer" formulation (Frankignoul et Hasselmann, 1977). This 2D horizontal model is implemented over the global ocean, using a near 100 km resolution, and integrated during a climatological year. Air-sea fluxes are taken from the ECMWF meteorological model (ERA40 reanalysis) and the surface currents are provided by altimeter data (SSALTO-DUACS analysis). The mixed layer depth (MLD) is derived from SST observations, using an original inversion technique. The MLD fields obtained from this inversion are well correlated to in situ estimates. This effective depth represents the air-sea fluxes penetration and ensures consistency between fluxes, les currents and SST. We first validate the simulation through examination of the heat balance in north-eastern Atlantic, by comparing to measurements and models from the POMME experiment. Then we study the salinity balance in the global domain, in terms of its geographical distribution and seasonal evolution. Equilibrium between the various processes appears generally more complex than for temperature. Noteworthy, the role of atmospheric flux is less predominant (22%), while geostrophic advection (33%) and diapycnal mixing (22%) contribute more strongly. Our results indicate this model succeeds in reconstructing SSS variability over most of the oceans. Daily SSS variations are also simulated, whereas they are not represented in current observed data at a global scale. Owing to its simplicity and fast computation, the model will be useful to the SMOS mission. It can help for the measurement calibration/validation and provide a first guess estimate to the sophisticated algorithm required for SSS restitution.
La salinité de surface des océans (SSS) influence de nombreux phénomènes océaniques, parmi lesquels la ventilation des eaux de surface, la formation d'eaux profondes et la circulation thermohaline. Elle détermine aussi certains processus couplés océan-atmosphère, notamment l'intensité du flux d'eau douce, la pénétration du flux de chaleur et de la turbulence. La mesure in situ de salinité est plus compliquée que celle de température, si bien qu'on dispose actuellement de 20 fois moins de données pour cette propriété. De plus, la température de surface (SST) est couramment estimée par satellite, ce qui n'est pas encore le cas de la SSS. Deux missions spatiales vont prochainement combler cette lacune : le satellite SMOS de l'Agence Spatiale Européenne et le satellite Aquarius/SAC-D de la NASA et de la CONAE. En préparation du projet SMOS, nous proposons une méthode pour estimer la SSS à partir des observations satellitaires actuelles et étudier les mécanismes de sa variabilité. Nous avons développé un modèle simplifié de couche mélangée océanique, basé sur la formulation "slab mixed layer" (Frankignoul et Hasselmann, 1977). Ce modèle 2D horizontal est implémenté sur l'océan global, avec une résolution proche de 100 km, et intégré au cours d'une année climatologique. Les flux air-mer proviennent du modèle météorologique ECMWF (réanalyse ERA40) et les courants de surface sont issus de l'altimétrie (analyse SSALTO-DUACS). La profondeur de la couche mélangée (MLD) est dérivée des observations de SST, grâce à une technique d'inversion originale. La MLD obtenue par inversion est bien corrélée aux estimations basées sur des données in situ. Cette profondeur effective représente la pénétration des flux air-mer et assure la cohérence entre les flux, les courants et la SST. La simulation est d'abord validée en examinant le bilan de chaleur dans l'Atlantique Nord-Est, par comparaison aux mesures et aux modèles de l'expérience POMME. Puis le bilan de salinité est étudié dans le domaine global, en termes de distribution géographique et d'évolution saisonnière. L'équilibre entre les différents processus est généralement plus complexe que pour la température. Notamment, le rôle du flux atmosphérique est moins prépondérant (22%), tandis que l'advection géostrophique (33%) et le mélange diapycnal (22%) contribuent fortement. Nos résultats montrent que ce modèle parvient à restituer la variabilité de la SSS sur la majeure partie des océans. Le modèle simule aussi les variations journalières de SSS, qui ne sont pas représentées à l'échelle globale dans les observations actuelles. Grâce à sa simplicité et à sa rapidité, le modèle pourra être utile dans le cadre de SMOS. Il pourra aider à la calibration/validation de la mesure et fournir une estimation a priori pour l'algorithme complexe nécessaire à la restitution de la SSS.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2006/these-2302.pdf
http://archimer.ifremer.fr/doc/00000/2302/